This invention relates generally to video signal processing systems and, more particularly, to such systems that are useful in the conversion of a conventional low-resolution video signal to a format suitable for subsequent transfer to high-resolution film.
Video processing equipment is now commonly used in the editing of video signals prior to their being transferred to motion picture film. Because such equipment operates on electronic representations of the video image, it provides far superior flexibility in the kinds of image processing that can be readily accomplished. Converting the image information to a digital format facilitates a convenient computer processing of the information to accomplish color enhancement, image mixing, special imaging effects processing, and various other known image manipulations. In addition, instantaneous visual feedback to the operator of the effects of the image processing enables the operator to make iterative processing changes and thereby provide the desired results quickly and efficiently.
Heretofore, video signal processing has not proven to be entirely satisfactory for use in situations where the final image product is intended to be high-resolution (e.g., 35 mm) film. This is because most video processing equipment operates on relatively low-resolution image data derived from NTSC-formatted video signals and the like. In the NTSC format, for example, only 525 lines of vertical resolution are provided. This is generally considered insufficient when transferred to film. Theater-quality film, for example, typically would require at least about 1000 to 2000 lines of vertical and horizontal resolution for a presentation picture of acceptable quality.
Efforts have been made in the past to increase the vertical and horizontal resolution of low-resolution video images; however, such efforts have not proven to be entirely successful. These resolution enhancement techniques generally involve interpolating lines for interleaving with the existing low-resolution lines and by interpolating pixels for interleaving with the original pixels of each line. The resulting high-resolution images are not always realistic replications of the original images. Frequently, objectionable artifacts arise, particularly when the image's time base is being modified, for example, from 60 fields per second to 24 frames per second. So-called aliasing problems can cause moving objects to acquire undesired jagged vertical edges.
It should therefore be appreciated that there is a need for a video image processing system that effectively converts video signals from a low-resolution format to a high-resolution format, for subsequent transfer to high-resolution film, without introducing artifacts or otherwise detracting from the image quality. Such a processing system ideally is adapted to reduce the image's frame rate and to convert the image from an interlaced to a non-interlaced video format, all while accurately preserving motion effects represented in the original video signal. The present invention fulfills these needs.